Pit heating furnace



Feb. 18, 1941. w. scHwlER PIT HEATING FURNACE Filed Aug. 30, 1959 Patented Feb. 1s, 1941 l ,UNITED STATES PATENT OFFICE PII HEATING FURNACE Wilhelm Schwier, Dusseldorf, Germany Application August 30, 1939, Serial No. 292,570 In Germany July 15, 1938 somma (ciao3-iai 'I'he present invention relates to pit heating furnaces and is particularly concerned with pit heating furnaces operating in zones. As compared tures in consideration,

nearly equal high temperatures exist in the working space and the material to be heated at any time and at all places, so that pit heating furnaces of this kind operate with high waste gas temperatures, bad heat utilization and high fuel consumption and are, due to the danger of cracks and aws occurring, useless for the cold insertion and particularly for hard material.

Annular heating furnaces having a rotatable hearth and a xed intermediate wall carrying burners as well as fixed waste gas pipes are known already. The rotatable mounting of the hearth,

however, offers great constructional dimculties due to the high load applied to the hearth which in case of pit heating furnaces may amount to tons and more.

As the ingots and slab ingots must be heated up to welding heat, the danger exists that the slag formed thereby smears the interior and exterior hearth gap causing stoppage of the plant in short time.

The pit heating furnace operating in zones as proposed according to the present invention obviates these drawbacks by the fact that for heating the furnace a travelling or rotatable ame of high ingress temperature and low egress temperature is used the local position of which relatively to the material to be heated and occupying a position of rest is altered in accordance with the progressive heating of the material and that, furthermore, the material to be heated is always inserted in the cold zone at the waste gas discharge end and is withdrawn from the hot zone in the same manner as in the case of gravity discharge furnaces and continuous heating furnaces with the difference, however,

that not the material to be heated but the heating means are travelling. Furthermore. the resulting slag may :freely flow olf towards both sides as in case of ordinary pit heating furnaces.

In the accompanying .drawing one construction according to the invention is shown by way of example.

In this drawing:

Fig. 1 is a cross-section through a pit heating furnace according to the invention, 5

Fig. 2 is a horizontal section through this furnace,

Fig. 3 is a top plan view of the furnace, and

Fig. 4 is a diagrammatic side view of the furnace showing the automatic control of the stationary burners.

In the annular pit heating furnace illustrated by way of example and having one chamber only, I designates the bottom, 2 the side walls, 3 the laterally arranged burners, 4 the slag holes, 6 the ingots to be heated standing on the bottom of the furnace and 6 a rotatable arched furnace roof which in a well known manner consists of individual carriages coupled together and having covers the wheels I of which carriages run on rails 8. Sealing cups 9 containing sand or liquid respectively and corresponding ledges I0 serve to seal the pit heating furnace against the surrounding atmosphere. In order to rotate the. roof a motor 32 is provided which is connected with a stationary part of the furnace. The gear I8 mounted on the motor shaft 32 engages the toothed rim 34 which is connected with the roof 6.

II also is a travelling end carriage having a bottom I2, side walls I3 and face walls I4 and I5 which form the movable or travelling face walls of the furnace and the closure towards the exterior atmosphere as well as the separation of the hot zone or the drawing end from the cold zone. or the insertion end respectively.

The movable intermediate member is provided with end wall burners I6, waste gas openings I'I, a motor driven gear I8 for the cover of the entire movable arched furnace roof, and a waste gas pipe I9 by way of which the waste gases are discharged into the central flue 29 and the chimney. A tank 30 is provided in the front part of the intermediate section supplying fuel to the burner I6 and a valve 29 is inserted in the conduit between the tank and the burner.

The material to be heated may be drawn progressively at the hot furnace end after removal of the cover 2I and may, after removal of the cover 22, be inserted at the cold furnace end by rotating the entire cover in the direction of the arrow about 5o the length'of always one section, whereby the same effect is obtained as if the material to be heated would continuously be conveyed through the furnace as is the case of gravity discharge furnaces and mechanical furnaces.

The lateral burners 3 arranged in the portion of the furnace not capable of being rotated are, during rotating of the cover, correspondingly controlled and cut in and out. They are provided preferably with an automatic control device. For this purpose a control strip 2l is connected with the rotatable roof 8 carried by the rollers 1. The control strip 24 consists of an upper and a lower section which are connected by an inclined section. The circumferential stationary burners I are provided with valves: vertically extending control levers 23 are connected with the valves.

- If the roof 8 rotates the control strip 24 impacts with its inclined section against the vertical con-` trol levers 23 and rotates the valves connected therewith. The burners are closed or opened by the rotation of the valves.

'Ihe levers 23 are returned in their original position by a suitable means. i According to the invention sealing is effected by maintaining excess pressure at thewall portions of the movable intermediate member, said excess pressure may be produced by blowing in hot combustion air by means of the laterally arranged burners present in the range of the intermediate member or by blowing into the gap hot waste gases which are withdrawn from the waste gas pipe by the heat exhauster 21 and compressed and forced through the pipes 28 into the gap, thus preventing hot and -incompletely burnt heating gases from being discharged by way of the gapl Y from the hot furnace end into the cold furnace end and into the chimney where they are lost. Sealing strips 25 and 26 are provided to further assist this procedure. Exhauster 21 is driven by the motor 3| and current is supplied to the latter by the current conductor 35.

The furnace according to the invention combines the advantages of the gravity discharge furnaces and the mechanical continuous heating furnaces with those of the pit heating furnaces the drawbacks or disadvantages of which are removed. The furnace forming the subject matter of the invention is mainly designed for heating ingots and slab ingots for rolling mills.

What I claim is:

1. A pit heating furnace comprising an annular -working chamber, a roof consisting of individual sections rotatable upon said chamber said sections successively forming the charging and discharging end of the furnace in correspondence with the advance of the roof and an intermediate section rotatable within said chamber the front end of said movable section in the direction of movement being provided with heating means and vthe opposite rear end with discharge means for the Waste gases from said working chamber.

2. A pit heating furnace comprising an annular working chamber, a roof consisting of individual sections rotatable on said chamber at least one of said sections forming the charging and at least another one of said sections forming the discharging end of the furnace in correspondence with the advance of the roof, removable covers for said sections and an intermediate section between the charging and the discharging end rotatable in said chamber said intermediate section being provided with heating and waste gas discharge means.

3.v A pit heating furnace comprising an annular working chamber having a bottom end and side walls, stationary burners at the circumference of said chamber. a roof consistingof individual sectionsrotatable on said chamber atleast one of said sections forming the charging and at least another one of s aid sections forming the dis- Ycharging end of the furnace, an intermediate section ybetween said charging and said discharging end rotatable in said chamber, said intermediate section being provided with` heating and waste gas discharge means and means connected with said rotatable roof to automatically control the operation of the stationary burners.

4. A pit heating furnace comprising an annular' working chamber, a roof consisting of individual sections rotatable upon said chamber at least one of said sections forming the charging and at least another one of said sections forming the discharging end of the furnace, an intermediate section.

a roof consisting of individual sections rotatable.

on said chamber at least one of said sections forming the charging and at least another one of said sections forming the discharging end of the furnace, an intermediate section rotatable in said chamber between said charging and said discharging end said intermediate section being provided with heating means and waste gas discharge means and means for creating in the gap between the said intermediate section and the chamber walls an excess gas pressure thereby preventing the entering of heating gases from said chamber into the waste gas connected charging end of the furnace.

6. A pit heating furnace according to claim 5, said excess gas pressure creating means consisting of means forcing waste gas into the gap between the intermediate section and the chamber walls.

WEHELM SCHWIER. 

